1. Field of Invention
This invention relates to a high purity, silicon dioxide (silica) refractory composition, castable composition and spray mix. The high purity silica refractory composition comprises from about 50.0 weight percent to 99.9 weight percent silicon dioxide and from about 0.1 weight percent to 30.0 weight percent of a binder. This invention also relates to a high purity silica refractory castable composition comprising the high purity silica refractory composition of the instant invention and water in an amount sufficient to achieve a castable composition consistency for casting the refractory castable composition with the use of forms.
Further, the present invention relates to an essentially non-slumping, pumpable and sprayable high purity silica refractory castable composition that may be applied without the use of forms comprising a tempered, pumpable first component comprising the refractory castable composition of the instant invention as disclosed herein, and a second component comprising at least one flocculating agent that is added to the first component at the time of installation of the sprayable high purity silica refractory castable composition in an amount to prevent slumping. A method of applying the essentially non-slumping, sprayable high purity silica refractory castable composition without the utilization of forms is provided.
2. Brief Description of the Background Art
U.S. Pat. Nos. 5,549,745 (Langenohl et al.) and 5,512,325 (Langenohl et al.) disclose a non-slumping, high density, low moisture sprayable refractory castable composition containing calcium aluminate cement. Thus, it will be appreciated by those persons skilled in the art that the use of low moisture, non-slumping, high density, and calcium aluminate cement containing refractory compositions that may be applied with and without forms are well-known.
It is well known that refractory bricks having a high silica content are employed to line the walls and surfaces of high temperature furnaces such as for example the furnaces used in glass tanks for the manufacture of glass and in coke ovens. Repair of worn silica refractory brick in high temperature furnaces has, up to the time of this invention, been limited to the replacement of the worn silica refractory brick from the wall or surface of the furnace, for example. The replacement of the worn silica refractory brick entails physically removing the worn silica refractory brick from the wall or surface and inserting a new silica refractory brick in place of the removed worn silica refractory brick. This procedure of replacing a worn high silica content refractory brick(s) with a new high silica content refractory brick(s) is very expensive due to the labor to replace the worn silica brick, the amount of time that the furnace is out of service and operation while being repaired, and the material costs. A monolithic refractory composition, therefore, is needed to repair a worn high purity silica refractory brick, and thus, eliminating the need to physically remove the worn high purity silica refractory brick from the surface of, for example a furnace wall, or glass tank crown.
Conventional and well known silica monolithic compositions and method(s) of applying the same are employed in lining various metallurgical vessels.
For example, U.S. Pat. No. 5,494,267 ( '267 Patent) discloses a pumpable refractory composition for manufacturing a refractory liner which is resistant to attack from slag comprising about 36 to 92 percent by weight silicon carbide, about 8 to 20 percent by weight of a binder which includes about 15 to 70 weight percent colloidal silica having an average particle diameter of 4 to 100 millimicrons, 0 to 10 percent by weight free carbon , and 0 to 50 percent by weight alumina. The refractory composition disclosed in the '267 Patent is cast into a liner shape with the use of forms and allowed to harden at room temperature. The '267 Patent states that the hardening takes from about fifteen minutes to five hours depending on the thickness of the desired refractory. The '267 Patent sets forth that the refractory composition preferably contains about ten to forty percent by weight of alumina and is preferably selected from brown fused alumina, white fused alumina, tabular alumina, and mixtures thereof U.S. Patent '267 states that the refractory composition preferably includes about 0.02 to 1.0 percent by weight of a setting agent such as calcium aluminate cement, magnesium oxide and mixtures thereof U.S. Patent '267 is unconcerned with providing a sprayable refractory composition that may be used without the use of forms. Further, U.S. Patent '267 is unconcerned with the particular unsolved problems that are encountered with high purity silica refractory brick in the volatile chemical environment of a glass-tank furnace.
While the above mentioned background art castable, refractory monolith compositions are known, they generally contain levels of calcium aluminate cement and alumina or contain low purity silica raw material that are unacceptable for use in replacing worn high purity silica refractory brick. The alumina content, low purity silica raw material, and combinations thereof, remain the weak links in employing known refractory castable monoliths to repair worn high purity silica refractory bricks in situ.
Therefore, in spite of this background material, there remains a very real and substantial need for a high purity silica refractory composition, and a castable composition, and a spray mix having a high purity silica refractory composition that may be employed for repairing worn high purity silica refractory bricks in situ.